J/A+A/648/A100 Massive G31.41+0.31 protocluster ALMA images (Beltran+, 2021)
Fragmentation in the massive G31.41+0.31 protocluster.
Beltran M.T., Rivilla V.M., Cesaroni R., Maud L.T., Galli D., Moscadelli L.,
Lorenzani A., Ahmadi A., Beuther H., Csengeri T., Etoka S., Goddi C.,
Klaassen P.D., Kuiper R., Kumar M.S.N., Peters P., Sanchez-Monge A.,
Schilke P., van der Tak F., Vig S., Zinnecker H.
<Astron. Astrophys. 648, A100 (2021)>
=2021A&A...648A.100B 2021A&A...648A.100B (SIMBAD/NED BibCode)
ADC_Keywords: Protostars ; Interstellar medium ; Interferometry
Keywords: ISM: individual objects: G31.41+0.31 - stars: formation -
stars: massive - techniques: interferometric
Abstract:
ALMA observations at 1.4mm and ∼0.2" (∼750au) angular resolution of
the Main core in the high-mass star forming region G31.41+0.31 have
revealed a puzzling scenario: on the one hand, the continuum emission
looks very homogeneous and the core appears to undergo solid-body
rotation, suggesting a monolithic core stabilized by the magnetic
field; on the other hand, rotation and infall speed up toward the core
center, where two massive embedded free-free continuum sources have
been detected, pointing to an unstable core having undergone
fragmentation.
To establish whether the Main core is indeed monolithic or its
homogeneous appearance is due to a combination of large dust opacity
and low angular resolution, we carried out millimeter observations at
higher angular resolution and different wavelengths.
We carried out ALMA observations at 1.4mm and 3.5mm that achieved
angular resolutions of ∼0.1" (∼375au) and ∼0.075" (∼280au),
respectively. VLA observations at 7mm and 1.3cm at even higher angular
resolution, ∼0.05" (∼190au) and ∼0.07" (∼260au), respectively, were
also carried out to better study the nature of the free-free continuum
sources detected in the core.
The millimeter continuum emission of the Main core has been clearly
resolved into at least four sources, A, B, C, and D, within 100,
indicating that the core is not monolithic. The deconvolved radii of
the dust emission of the sources, estimated at 3.5mm, are 400-500au,
their masses range from 15 to ∼26M☉, and their number densities
are several 109cm-3. Sources A and B, located closer to the center
of the core and separated by 750au, are clearly associated with two
free-free continuum sources, likely thermal radio jets, and are the
brightest in the core. The spectral energy distribution of these two
sources and their masses and sizes are similar and suggest a common
origin. Source C has not been detected at centimeter wavelengths,
while source D has been clearly detected at 1.3cm. The fact that
source D is likely the driving source of an E-W SiO outflow
previously detected in the region suggests that the free-free emission
is possibly arising from a radio jet.
The observations have confirmed that the Main core in G31.41+0.31 is
collapsing, has undergone fragmentation and that its homogeneous
appearance previously observed at short wavelengths is a consequence
of both large dust opacity and insufficient angular resolution. The
low level of fragmentation together with the fact that the core is
moderately magnetically supercritical, suggests that G31.41+0.31 could
have undergone a phase of magnetically-regulated evolution
characterized by a reduced fragmentation efficiency, eventually
leading to the formation of a small number of relatively massive dense
cores.
Description:
Interferometric observations of G31.41+0.31 at 1.4mm in Band 6 and
3.5mm in Band 3 were carried out with ALMA in Cycle 4 and Cycle 6 as
part of projects 2016.1.00223.S (P.I.: M. Beltran) and 2018.1.00252.S
(P.I.: M. Beltran). Observations at 1.4mm were carried out in one of
the more extended configurations, C40-7. The 1.4mm observations were
combined with those of the ALMA Cycle 2 project 2013.1.00489.S (P.I.:
R. Cesaroni), which were observed in the extended C34-7/(6)
configuration and with the same digital correlator configuration.
The files are the ALMA and VLA data used to produce the maps in Figs.
1, 2, 3, 4, and 6. Units are Jy/beam. Coordinate system is equatorial
(J2000.0).
Objects:
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RA (2000) DE Designation(s)
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18 47 34.315 -01 12 47.0 G31.41+0.31 = MSX6C G031.4134+00.3092
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 137 4 List of fits images
fits/* . 4 Individual fits images
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See also:
J/A+A/598/A59 : G31.41+0.31 SMA spectra (Rivilla+, 2017)
J/A+A/630/A54 : G31.41+0.31 Stokes IQU images (Beltran+, 2019)
J/A+A/641/A54 : Complex organic molecules in high-mass SFRs (Coletta+, 2020)
J/A+A/644/A84 : GUAPOS. identified transitions of C2H4O2 (Mininni+, 2020)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 23 I4 --- Nx Number of pixels along X-axis
25- 28 I4 --- Ny Number of pixels along Y-axis
30- 52 A23 "datime" Obs.date Observation date
54- 58 I5 Kibyte size Size of FITS file
60-112 A53 --- FileName Name of FITS file, in subdirectory fits
114-137 A24 --- Title Title of the FITS file
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Acknowledgements:
Maria T. Beltran, maria.beltran(at)inaf.it
(End) Patricia Vannier [CDS] 17-Mar-2021